1. Field of the Invention
The invention relates to a water preheating connection piece with at least one heating rod that has an internal heating element and a heating rod which is adapted for connection to the water preheating connection piece.
2. Description of the Related Art
Water preheating connection pieces are known in which glow plugs having a glow plug body with external threads and a hexagonal nut for screwing-in are screwed into a drill-hole of a preheating connection piece, the drill-hole being provided with an internal thread that cooperate with the external threads of the glow plug body.
For instance, FIGS. 4(a) and (b) show a conventional water preheating connection piece 9 with fitted glow plugs 8 with a glow plug body, having an external thread and a hexagonal nut 10 for screwing into drill-holes of the connection piece 9 with corresponding internal threads. Such a design, however, is disadvantageous in that the overall weight is large, and thus, it becomes susceptible to breakage due to vibrations in the case of its use in motor vehicles and also increases the likelihood of improper sealing at the threads.
An object of the present invention is to provide a water preheating connection piece and a heating rod for the water preheating connection piece which can be economically manufactured. The water preheating connection piece and a heating rod in accordance with the present invention is lightweight and provides a more rigid connection while, at the same time, reducing the risk of breakage due to vibration.
The problems associated with conventional water preheating connection pieces are solved in accordance with the present invention by providing a water preheating connection piece with at least one heating rod having an internal heating element, and optionally, at least one regulating element, the heating rod projecting into a water through-flow channel. The heating rod is designed without an external thread, and thus, is press-fit into a threadless drill-hole of the water preheating connection piece. A connection pole projects from the heating rod and is electrically insulated against the casing of the heating rod.
Instead of being press-fit into the drill-hole of the water preheating connection piece, an adhesive such as glue may be used to connect the heating rod to the drill-hole such that a sealing edge that encircles the heating rod is preferably formed on the heating rod. The drill-hole of the water preheating connection piece is also provided with a circumferential sealing edge.